This invention relates to switching mode regulators using pulse width modulation.
Switching regulators have been used for both high and low voltage power supply designs for many years. The circuit includes a series transistor which is switched on and off by a pulse width modulator. Direct coupled drive between the modulator and the switching transistor has been avoided, especially when a three-phase A.C. supply is used, because it requires an isolation transformer for the primary power so that one side of the rectified supply can be grounded. This transformer adds considerable weight and volume to the design and has been avoided in favor of various A.C. coupled designs. While this has proven to be an effective means of reducing weight and volume, the need to reset cores or discharge capacitors has limited the duty cycle to approximately 80%. This increases the peak current requirements of the switches without reducing the voltage requirements and, therefore, limits the power handling capability of available transistors.
New switching regulator designs are now using the recently available high power, high voltage FET's (field effect transistors) in an effort to decrease switching times and increase operating frequencies so that dissipated power, size, and weight can be reduced.